Confusing exception info in Flink-SQL

[徐涛]

Hi Experts,

When I am using the following sentence in Flink-SQL

if(item_name=‘xxx',u.user_id,null)

The following exception was throw out, which is a bit confusing, because it is actually caused by there is no if function in Flink-SQL, I think it is more clearly to just point it out that there is no if function, is it?

Caused by: org.apache.calcite.runtime.CalciteContextException: From line 1, column 90 to line 1, column 93: Illegal use of 'NULL'
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
	at org.apache.calcite.runtime.Resources$ExInstWithCause.ex(Resources.java:463)
	at org.apache.calcite.sql.SqlUtil.newContextException(SqlUtil.java:783)
	at org.apache.calcite.sql.SqlUtil.newContextException(SqlUtil.java:768)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.newValidationError(SqlValidatorImpl.java:4759)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.inferUnknownTypes(SqlValidatorImpl.java:1727)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.inferUnknownTypes(SqlValidatorImpl.java:1804)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.inferUnknownTypes(SqlValidatorImpl.java:1804)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.inferUnknownTypes(SqlValidatorImpl.java:1804)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.expandSelectItem(SqlValidatorImpl.java:456)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateSelectList(SqlValidatorImpl.java:4023)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateSelect(SqlValidatorImpl.java:3286)
	at org.apache.calcite.sql.validate.SelectNamespace.validateImpl(SelectNamespace.java:60)
	at org.apache.calcite.sql.validate.AbstractNamespace.validate(AbstractNamespace.java:84)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateNamespace(SqlValidatorImpl.java:967)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateQuery(SqlValidatorImpl.java:943)
	at org.apache.calcite.sql.validate.SetopNamespace.validateImpl(SetopNamespace.java:102)
	at org.apache.calcite.sql.validate.AbstractNamespace.validate(AbstractNamespace.java:84)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateNamespace(SqlValidatorImpl.java:967)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateQuery(SqlValidatorImpl.java:943)
	at org.apache.calcite.sql.validate.SetopNamespace.validateImpl(SetopNamespace.java:102)
	at org.apache.calcite.sql.validate.AbstractNamespace.validate(AbstractNamespace.java:84)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateNamespace(SqlValidatorImpl.java:967)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateQuery(SqlValidatorImpl.java:943)
	at org.apache.calcite.sql.SqlSetOperator.validateCall(SqlSetOperator.java:90)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateCall(SqlValidatorImpl.java:5187)
	at org.apache.calcite.sql.SqlCall.validate(SqlCall.java:115)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validateScopedExpression(SqlValidatorImpl.java:918)
	at org.apache.calcite.sql.validate.SqlValidatorImpl.validate(SqlValidatorImpl.java:628)
	at org.apache.flink.table.calcite.FlinkPlannerImpl.validate(FlinkPlannerImpl.scala:105)

Best

Henry